Roller bit



June 6, 1967 A. GRAFER ETAL 3,323,605 I ROLLER BIT Filed Feb. l 1965 INVENTORTS ALBRECHT GRAFER.

ALFRED PILGRIM 0L, Z BY ATTOR United States Patent 40, both of Sprockhovel, Westphalia, Germany Filed Feb. 12, 1965, Ser. No. 432,184 4 Claims. (Cl. 175366) This invention relates to a new roller bit which is particularly adapted for the purpose of widening boreholes to large diameters. The bit of the present invention is simpler to manufacture than those of the prior art and has an improved bearing for the cutting rollers, and seals therefor, and makes possible a simple replacement of damaged parts at the drilling site.

There has been significant development within recent years in the technique of drilling large boreholes and, at the present time, boreholes with diameters in excess of one meter and lengths in excess of two hundred meters can be made even in hard rock formations.

This technique has been successfully employed particularly in underground mining installations Where boreholes are used as rough or advance drilling holes for sinking shafts and sumps, and as cable or ventilation tunnels. It has been found that the most economical drilling method consists in making a rough or advance borehole which is subsequently widened to the desired final diameter in one or several drilling stages.

The drilling bits used for this purpose operate almost exclusively according to the principle of hob cutting tools and are known as roller rock bits. Such roller bits used for widening boreholes generally consist of one central body member having arms radially mounted thereon, which arms include the axes about which the cutting rollers rotate.

In bits heretofore known, only a single roller bearing is used almost exclusively for supporting or positioning the cutting rollers. In cutting rollers having small diameters, ball bearings and/ or roller bearings are mounted between the correspondingly shaped or developed axis and the inner bore of the cutting roller, while in cutting rollers having larger diameters, independent roller bearings may be employed. A particular problem is encountered in connection with sealing the bearing while flushing the borehole, irrespective of whether the flushing is effected with a liquid or with compressed air. Numerous patents and publications are directed to the structure and configuration of the bearings or the sealing thereof but all of the various types and designs heretofore known are subject to various difiiculties and drawbacks.

In addition to the very high manufacturing costs resulting from the required small bearing tolerance, which influence the economy of the drilling operation, the insufiicient durability or working life and the high susceptibility to malfunction during drilling predominately impede a more significant expansion of the technique of drilling large boreholes. Further, complaints have been made because of damage to the cutting rollers or the bearings thereof which, is of necessity, unavoidable in the course of underground drilling operations. Repair or exchange of the damaged portions at the drilling site can be effected only with difiiculty or not at all and the entire drill bit must, instead, be transported to a workshop having the proper repair equipment.

In accordance with the present invention, a roller bit is provided which is particularly adapted for the purpose of widening boreholes to large diameters. The bit of the present invention is simpler to manufacture than those of the prior art and has an improved bearing for the cutting rollers, and seals therefor, and makes possible a simple replacement of damaged parts at the drilling site. In the bit of the present invention, rotatable shafts are mounted in radial supporting arms on a central body and the outwardly projecting ends of these rotatable shafts support the cutting rollers.

The cutting roller is reduced to a very simple device which may be inexpensively manufactured and which is easy to replace. The bearing has been removed from the cutting roller and mounted in the supporting arm where it can be made larger and thereby more resistant to wear. Further, it can be sealed against fouling in a greatly improved manner.

A further advantage of the present invention resides in the fact that the supporting arms are easily detachably mounted on the central body of the roller bit, for example by means of flange-like configurations of the connecting surfaces at the supporting arms and the central body and by means of a split fastening or retaining ring. As a result of the separate provision and easy removability of the supporting arms it, is possible not only to effect a replacement in the case of damage easily and rapidly, but the drilling bit may be transported to and from the drilling site in separate individual parts. Specifically, for the purpose of making boreholes having large diameters, this particular provision represents an essential advantage as compared to the heretofore customary drilling bits which were made in a single piece.

The construction of the present invention also includes a flushing duct passing through each of the rotatable shafts mounted in each of the supporting arms, which duct connects with an annular chamber in each of the toothed rollers, the latter chamber being in communication with a plurality of radial bores which discharge at the bottom of the gaps between the teeth in the cutting roller. It is, thus, possible to freely flush the borehole from ducts between the roller teeth, whereas this could heretofore be effected only from the outside.

It is also possible in the present invention to use the same means of connection as is employed to connect the supporting arms to the central body to assemble several roller bits in a combined drilling device. In such a construction, the central body is provided with a flangelike configuration, with adjusting springs between the separate portions for transmitting the torsional moment. The flange-like configuration provides a readily detachable connection and the flanges may be secured together by means of a split clamping ring for example. In this way, a number of roller drill bits can be connected together. Thus, the combination of several roller bits to form one composite widening or enlarging bit becomes very simple.

The invention will be further illustrated by reference to the accompanying drawing in which a roller bit according to the present invention is shown, partially in section.

Referring to the drawing, the central body member 1 has an easily detachable supporting arm 2 connected thereto. The arm 2 may be mounted on the central body 1 in any desired number. The elements 1 and 2 are secured together by the split retaining ring 3 which latter is held together by the machine bolt and nut 23. A cutting roller 4 is mounted on the rotatable shaft 6, which latter is supported by the ball bearings 5 in the supporting arm 2.

As will be seen from the drawing, there is sufficient space in the supporting arm 2 so that the bearings 5 may have any desired dimensions and may be sealed off with absolute assurance and safety. Accordingly, it is possible to design and provide the cutting roller 4, which is subjected to direct wear and tear, so that it is easily replaceable. In the embodiment shown, the cutting roller contains only one smooth cylindrical bore 7 which receives the end 18 of the rotatable shaft 6. A snap ring 8 prevents the cutting roller from sliding off the end of the shaft 6. Also, the central body member 1 and the supporting arm 2 constitute independent units which may be individually replaced in the case of damage and which may also be separated for easier transportation thereof. They are connected together in a simple manner by means of the flange-like configuration 21 of both parts and the split fastening ring 3.

Flushing medium is passed through a central bore 9 in the central body member 1, then into the bore 10 in the shaft 6, then through the annular chamber 20 in the roller 4, and then through the radial bores 11 which discharge at the bottom of the gaps between the teeth on the roller 4 and, thus, prevent the gaps between the teeth from being plugged. Accordingly, it is immaterial whether the rollers have a helical gear tooth system or a ring tooth system. Further, the bottom of the borehole is directly flushed by flushing medium passing through the transverse bores 12 in the shaft 16. The seals 13 and 14 prevent the flushing medium from entering the bearings and also prevent the bearing lubricant from running out. An annular relief chamber, together with the discharge bore 15, is provided in case any flushing medium should penetrate through the seal 13. Different structural arrangements can, of course, be employed to perform this function such as, for example, the provision of an additional duct extending through the shaft 6.

The design and construction of the present invention provides for the use of several rings of cutting rollers in different planes being mounted above and below one another and having cutting diameters which become progressively larger or smaller, respectively. The connection of the individual members 1 and 24 with one another is effected at 22 by means of a split fastening ring 16 which is held together by machine bolts and nuts, not shown. Adjusting springs 17 are mounted between the individual members 1 and 24, the latter being a drill string, in order to transmit the torsional moment. With an increasing diameter of the borehole, the cutting rollers l 4 become correspondingly larger in diameter. Advantage may be taken of this in the construction of the present invention in that worn cutting rollers are reused for smaller borehole diameters by machining new cutting teeth thereon.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A roller bit comprising a central body, a plurality of hollow arms detachably mounted on the body, a rotatable shaft mounted in bearings located in each of said arms, and a toothed roller secured on each rotatable shaft.

2. A roller bit according to claim 1 in which each of the arms is provided with a flange which abuts against a flange on the central body, the flanges being secured together by a fastening ring.

3. A roller bit according to claim 1 in which each rotatable shaft has a flushing duct therein which connects with an annular chamber and a plurality of radial ducts in each roller.

4. A roller bit according to claim 3 in which the radial ducts discharge between the teeth on the roller.

References Cited UNITED STATES PATENTS 1,200,935 10/1916 Gerdes -354 2,038,388 4/1936 Sherman 175354 2,039,551 5/1936 Phipps 175354 2,370,070 2/1945 Phipps 175 -354 3,016,099 1/1962 Woodruff 175344 CHARLES E. OCONNELL, Primary Examiner.

N. C. BYERS, Assistant Examiner. 

1. A ROLLER BIT COMPRISING A CENTRAL BODY, A PLURALITY OF HOLLOW ARMS DETACHABLY MOUNTED ON THE BODY, A ROTATABLE SHAFT MOUNTED IN BEARINGS LOCATED IN EACH OF SAID ARMS, AND A TOOTHED ROLLER SECURED ON EACH ROTATABLE SHAFT. 